In conventional elevators, there are various types of drives systems to select from. These systems include among them traction rope drive systems, hydraulic drive systems, and linear motor drive systems. The required rise of the elevator system is one determining factor in selecting a drive system. The latter two drive systems are significantly limited in rise due to the physical limitations of the hydraulic cylinder and the electrical stator, respectively. Rope traction systems permit much higher rises, however, they are also limited by the physical limitations of the ropes used. At a determinable length, a rope will fail under its own weight.
Another factor in the selection of the drive system for an elevator is the cost of the system. These costs include material costs, installation costs and operating costs. One suggestion to reduce the installation costs of the elevator system is to modularize the hoistway components. This has been suggested in commonly assigned European Patent Application 0 442 230. This application discloses a modular arrangement for the car guide rails, the counterweight guide rails and various other hoistway components. As a result of the modularity, much of the hoistway structure can be prefabricated and shipped to the building site for installation as a preassembled module.
The above art notwithstanding, scientists and engineers under the direction of Applicants' Assignee are working to develop improved drive mechanisms for passenger conveyors that are not subject to the conventional limitations and that minimize operating and installation costs.